Atomic Structure and the Periodic Table Overview

Atomic number

Number of protons

Mass number

Number of protons + neutrons

Relative Atomic Mass (Ar)

An average value that takes account of the abundance of the isotopes of an element

Ar formula

(mass 1 x abundance 1) + (mass 2 x abundance 2)

Radius of atom

10^-10 m

Radius of nucleus

10^-14 m

Electron shell

Each shell can hold a maximum number of electrons

1st shell maximum electrons

2

2nd shell maximum electrons

8

3rd shell maximum electrons

8

Proton

Sub-atomic particle with a relative mass of 1 and a charge of +1

Neutron

Sub-atomic particle with a relative mass of 1 and no charge

Electron

Sub-atomic particle with a relative mass of very small and a charge of -1

Element

Consists of one type of atom only

Compound

Formed from chemically bonding elements

Mixture

Two or more elements or compounds not chemically bonded together

Ion

An atom or molecule which has different number of protons and electrons

Isotope

Atoms of the same element with the same number of protons but different numbers of neutrons

Abundance

How much of something there is (as a percentage)

Periodic table

Lists all the known elements in order of increasing atomic number

Metals

Elements that react to form positive ions

Alkali metals

A group of metals in the periodic table

Alkali earth metals

A group of metals in the periodic table

Non-metals

Elements that do not form positive ions and typically have properties such as being soft, low density, and having low melting and boiling points.

Metallic properties

Characteristics of metals, including the ability to conduct electricity and heat, and being shiny when cut.

Non-metallic properties

Characteristics of non-metals, including being dull, poor conductors of heat and electricity, and brittle.

Group number

The column number in the periodic table that indicates the number of electrons in the outermost shell.

Period number

The row number in the periodic table that indicates the number of shells containing electrons.

Group

A column of elements in the periodic table with similar chemical properties.

Group 7 Halogens

Elements in Group 7 of the periodic table that have 7 electrons in their outermost shell and increase in reactivity down the group.

Diatomic molecules

Molecules made of two atoms combined, such as F2 and Cl2.

Periodic table development

The arrangement of elements by atomic mass in the early 1800s that revealed a periodic pattern in properties.

Newland's Octaves

A method proposed by Newland in 1863 where every eighth element had similar properties, which was unsuccessful due to gaps left for undiscovered elements.

Dimitri Mendeleev

A scientist who created a periodic table in 1869 ordered by atomic mass, leaving gaps for undiscovered elements whose properties fit the patterns.

Reactivity trend in groups

Reactivity increases down the group for alkali metals and increases up the group for halogens.

Group 0 Noble Gases

Elements in Group 0 that are unreactive/inert due to having a stable arrangement of electrons and a full outer shell.

Displacement reactions

Reactions where a more reactive halogen displaces a less reactive halide ion from its solution.

Boiling point trend

Boiling points increase down the group for noble gases.

Reaction with oxygen

Alkali metals react with oxygen to form alkali metal oxides.

Reaction with water

Alkali metals react with water to form alkali metal hydroxides and hydrogen.

Reaction with chlorine

Alkali metals react with chlorine to form alkali metal chlorides.

alloy

a mixture of two or more elements, at least one of which is a metal

covalent bond

the bond between two atoms that share one or more pairs of electrons

covalent bonding

the attraction between two atoms that share one or more pairs of electrons

delocalised electron

bonding electron that is no longer associated with any one particular atom

dot and cross diagram

a drawing to show only the arrangement of outer shell electrons of the atoms or ions in a substance

fullerene

form of the element carbon that can exist as large cage-like structures, based on hexagonal rings of carbon atoms

gases

substances that have no fixed shape or volume and can be compressed easily

giant covalent structure

a huge 3D network of covalently bonded atoms

giant lattice

a huge 3D network of atoms or ions

giant structure

see giant lattice

intermolecular forces

the attraction between the individual molecules in a covalently bonded substance

ionic bond

the electrostatic force of attraction between positively and negatively charged ions

liquids

substances that have a fixed volume, but they can flow and change their shape

nanoscience

the study of very tiny particles or structures between 1 and 100 nanometres in size - where 1 nanometre = 10-9 metres

particle theory

a theory that explains the properties of solids, liquids and gases based on the fact that all matter is made from tiny particles. It describes the movement of particles and the distance between them

polymer

a substance made from very large molecules made up of many repeating units

solids

substances that have a fixed shape and volume that cannot be compressed

states of matter

the forms in which matter can exist. A substance can be solid, liquid or gas